In slaughterhouses, where slaughter animals suspended from product carriers of a conveying device are processed, there is a continuous pursuit of increasing the capacity. Modern slaughter lines for slaughter birds are capable of processing typically at least 12,000 birds per hour, for example, but even higher capacities are considered to be desirable with a view to reducing the cost involved in the processing of slaughter birds. Various possibilities, whether or not in combination with each other, are available for increasing the capacity of a slaughterhouse. A first possibility is to increase the speed of the conveying device by means of which the slaughter animals are conveyed through a slaughterhouse, during which conveyance the slaughter animals are processed. A second possibility is to reduce the pitch between successive product carriers. In slaughterhouses it may for several reasons be necessary to selectively remove slaughter animals, such as birds, from a product carrier at the location of a processing position. The term “selective” indicates that only selected slaughter animals are to be removed from the product carrier at the location of the processing position, whilst for example the slaughter animals in an adjacent upstream product carrier and an adjacent downstream product carrier must not be removed from said product carrier at the location of said processing position. Such a selection may for example take place on the basis of the weight of the slaughter animal or on the basis of a visual assessment of a slaughter animal. A transfer situation may occur, in which a slaughter animal is transferred from one product carrier to another product carrier. Alternatively, specific slaughter animals may fall from a product carrier into a collecting bin or onto a further conveyor, such as a belt conveyor.
When relatively high speeds of the conveying device are used, there is an increased risk that the at least one held part of slaughter animals will slip out of the at least one groove of a product carrier, in particular in bends in the conveying line. For that reason it may be desirable to use a relatively large angle between a horizontal line and the direction of inclination, being the direction in which the at least one groove extends, and/or to use a relatively long groove. Alternatively, or in combination, it is also conceivable to dimension and/or configure the grooves to have a slight local constriction of the width of the grooves, so that the held parts, such as typically a bird's legs in the case of birds, are held in the lower end of a groove with a slight clamping fit and/or a more or less form-locked fit.
All the above possible aspects connected with increasing the capacity of a slaughterhouse in themselves make it more difficult to selectively remove slaughter animals from a product carrier. On the one hand this is the case because the use of product carriers that may have been adapted in the above-described manner with a view to realising higher line speeds makes it more difficult to remove slaughter animals from the product carriers, whilst on the other hand higher line speeds and or smaller pitches increase the risk that a pusher element by means of which a slaughter animal is removed from a product carrier, more specifically by means of which the at least one held part of a slaughter animal is pushed out of at least one slot of a product carrier, will undesirably collide with a slaughter animal suspended from an adjacent upstream or downstream product carrier. Accelerating the stroke of the pusher element will increase the impulse that acts on the at least one held part of the slaughter animal, so that there is an increased risk of damage to the slaughter animal and of undesirable bone fractures.
European publication EP 1 922 935 A1 describes a combination according to the introduction, wherein the moving means comprise a stepping motor or a servomotor and wherein it is possible to impart a movement or speed pattern to the pusher element, which is claimed to make the combination more suitable for high-speed operation. Apart from the fact that this is a relatively costly solution, the magnitude of the positive effect that may be achieved is moreover limited.